A new asymmetric transesterification of secondary alcohols catalyzed by feruloyl esterase from Humicola insolens has been found. Although alcohols are not the natural substrates for this enzyme, a high R enantioselectivity was observed. Stereochemical studies showed that variations in substrate structure lead to strong variations in enantioselectivity. The highest enantioselectivities are obtained when the beta-carbon of the secondary alcohol is tertiary or quaternary.
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http://dx.doi.org/10.1016/j.bioorg.2005.05.002 | DOI Listing |
Nitrones are widely used as 1,3-dipoles in organic synthesis, but control of their reactions is not always easy. This review outlines our efforts to make the reactions of nitrones more predictable and easier to use. These efforts can be categorized into (1) 1,3-nucleophilic addition reaction of ketene silyl acetals to nitrones, (2) geometry-controlled cycloaddition of C-alkoxycarbonyl nitrones, (3) stereo-controlled cycloaddition using double asymmetric induction, and (4) generation of nitrones by N-selective modification of oximes.
View Article and Find Full Text PDFBiomacromolecules
July 2024
Department of Chemistry and Biology "Adolfo Zambelli" University of Salerno, via Giovanni Paolo II, 132, 84084 Fisciano, SA, Italy.
A backbone-substituted N-heterocyclic carbene (NHC) zinc complex, in combination with alcohol initiators, has been shown to be an effective catalyst for the ring-opening polymerization (ROP) of trimethylene carbonate (TMC) to poly(trimethylene carbonate) (PTMC) devoid of oxetane linkages. The ROP of TMC proceeded in solution to give PTMC, possessing controlled molecular mass (2500 < < 10000) and low dispersity ( ∼ 1.2).
View Article and Find Full Text PDFOrg Biomol Chem
June 2024
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
Asymmetric total synthesis of two naturally occurring resorcylic acid lactones (RALs), hamigeromycins F and G, was achieved for the first time. The synthetic strategy involved a late-stage intramolecular macrolactonization achieved with a transesterification reaction. Stereocenters (C and C) in both the molecules were accessed an enzymatic kinetic resolution reaction.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
May 2024
State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, and Chemical Biology Center, Peking University, 38 Xueyuan Road, Beijing, 100191, P. R. China.
We have achieved the first total synthesis of pallamolides A-E. Of these compounds, pallamolides B-E possess intriguing tetracyclic skeletons with novel intramolecular transesterifications. Key transformations include highly diastereoselective sequential Michael addition reactions to construct the bicyclo[2.
View Article and Find Full Text PDFChemistry
February 2024
College of Chemical and Biological Engineering, Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology, Zhejiang University, 310027, Hangzhou, P. R. China.
A novel method to prepare asymmetric amine ethers is reported. Tertiary amine alcohol hydrogen sulfate intermediates are prepared through a reactive distillation process, followed by the transesterification process to afford eventually asymmetric amine ethers. Experiments and DFT calculations revealed the essential roles the sulfate group plays in the highly selective monoesterification process.
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